1. Field of the Invention
The present invention is related to the design process of composite laminates, and more particularly, to a method for optimizing a stacking sequence for composite laminates with multiple zones having different numbers of plies.
2. Description of Related Art
Composite laminates are structures created by laminating two or more plies together such that the cumulative properties of the composite laminate are superior to the individual properties of the plies. Composite laminates are commonly used throughout industry, particularly the aerospace industry, because of their engineering qualities, design flexibility, and low weight. The vertical, or “through the thickness,” arrangement, also called the stacking sequence, of the individual plies in the laminate is an important consideration in the design and manufacture of composite structures. Plies having a variety of properties, such as material and fiber orientation, must be oriented and sequenced in an optimal arrangement to provide the optimal structural performance. Furthermore, composite laminates may include multiple zones across the length and width of the part, or horizontal direction, wherein the zones have requirements for different numbers of plies of each of the materials and fiber orientations used within the part.
Sequencing of plies of a composite laminate in the horizontal and vertical directions is well known in the art. U.S. Pat. No. 5,984,511 to Vasey-Glandon et al. (“the '511 patent”) discloses a knowledge driven composite design optimization process to sequence plies of a composite laminate. The '511 patent discloses techniques to optimize ply stacking horizontally across a composite laminate. However, the '511 patent does not discuss how to optimize a vertical stack of the plies based on structural rules such that the plies will be arranged for structural and cost considerations. In addition, the '511 patent discloses heuristic-based methods of sequencing the plies of a composite laminate, which implement a predetermined suite of solution procedures specifically designed for a particular kind of composite part and which lack the flexibility of prioritizing different design rules in the solution procedure.
Composite laminates having multiple zones will include internal ply edges within the composite laminate. Internal ply edges, which are also known as terminating edges, are the terminating or initiating edges of a ply, which usually occur along the boundary of a zone. The arrangement of internal ply edges is dependent on both horizontal and vertical combinations of the zone requirements into plies within the laminate. Poor placement of internal ply edges can increase the manufacturing costs for composite laminates having multiple zones. Accordingly, it is desirable to have a sequencing process that properly minimizes the internal ply edges between plies of a composite laminate. Therefore, a need exists for a process to optimize the stacking sequence of a composite laminate having multiple zones to reduce the internal ply edges.